U.S. Pat. No. 3,825,470 to Elbert et al is illustrative of transfer mediums suited to lift-off correction. As there disclosed, the ink printed must be coherent as printed and be cohesive to itself in preference to the paper printed upon during the lift-off step. An element having an adhesive surface is impacted against a printed character to be eradicated and the element is pulled away.
Preferred embodiments of this invention employ a material in the correction medium whih is very similar chemically to a moiety of the body of the ink to be eradicated. A teaching employing such a mechansim in lift-off correction is in the IBM Technical Disclosure Bulletin article entitled"Tackified Correctable Inks," by C. W. Anderson and H. T. Findlay, Vol. 23, No. 12, May 1981, at page 5461. That teaches the addition of methyl ester of natural resin to the adhesive element and to the ink.
Radiation hardening of polymerizable polymers to form laminations is known in the art in various forms. U.S. Pat. No. 3,754,966 to Newman et al is illustrative. That patent is of particular interest because it discloses trimethylol propane triacrylate as a major polymerizable ingredient. That acrylate is a major ingredient of preferred embodiments of this invention. The patent, however, teaches a transfer medium, not a lift-off correction medium. This invention employs a polyacidic fatty acid as a major ingredient, an ingredient much different from the unsaturated polymers and polymerizable monomers employed as a second resin-forming ingredient in that patent.
Use of ultraviolet radiation to form lamination is a standard technique. U.S. Pat. No. 3,770,490 to Parker is illustrative. It is also of particular interest because it disclosed trimethylol propane triacrylate as a polymerizable ingredient. That patent is directed to container coatings and does not employ a polyacidic fatty acid as an ingredient.
The following patents specifically mention achieving adhesives for correction in which necessary adhesive properties for lift-off correction are produced at impact: German Pat. No. 24 12 037 published May 5, 1977; U.S. Pat. No. 4,093,772 to Taylor et al, and United Kingdom Pat. No. 2,006,235 published May 2, 1979. The German and United Kingdom patents disclose the use of acrylate resins, but not a triacrylate. The United Kingdom patent also discloses the use of dimer acids. The U.S. patent employs polyamide in the bonding layer which is the same polyamide as that used in commercial inks. This is said to provide good compatibility and adhesion. None employ ionizing radiation hardening.
An inherent and well recognized advantage of radiation hardening to obtain a final product is that no materials are expelled from the product which might find their way into the atmosphere and act as a pollutant. In a solvent-applied process, for example, solvent must be recovered to prevent it from going into the atmosphere and such recovery may be imperfect even when the most advanced and expensive recovery equipment is employed. The foregoing and other prior art known does not encompass a lift-off correction medium made by ionizing radiation hardening.